 Nimotrelvir, an oral drug used to treat COVID-19, has been found to reduce the risk of progressing to severe cases of the virus. However, it may also have a negative effect on the body's ability to develop antibodies and T-cells specific to the virus. This could lead to relapses after treatment is completed, as seen in some patients. This article was authored by Valeria Fumigoli, Pietro di Lucia, Michael Rava, and others.